A nitrificação biológica em meio salino foi investigada em sistema contínuo, a partir de um efluente sintético contendo 152,44 mg L-1 de nitrogênio amoniacal total. Os testes com adição de concentrações crescentes de sal (100, 250, 500, 1.000, 2.000, 4.000, 8.000, 10.000 e 15.000 mg Cl- L-1) foram realizados em um biorreator em escala de laboratório de 5,7 L. Neste estudo, o objetivo foi avaliar a resposta da técnica de respirometria na identificação da toxicidade da biomassa nitrificante em diferentes concentrações salinas. Durante o período experimental, o biorreator operou com o tempo de retenção hidráulica de 48h e valores de OD, pH e temperatura foram mantidos em 4,0-5,0 mg L-1, 7,5 e 25°-30°C, respectivamente. Os ensaios de respirometria foram realizados em triplicata, com a utilização da sonda de oxigênio dissolvido. Os resultados da respirometria constataram que ambas as taxas de consumo de oxigênio (OUR) e de consumo especifico de oxigênio (SOUR) aumentaram até a concentração de 1.000 mg Cl- L-1, quando o máximo de eficiência de nitrificação de 65,18% foi obtida com aproximadamente 90 dias de operação do sistema. No entanto, o aumento gradual a partir de 2.000 mg Cl- L-1, resultou na queda dos valores de consumo de oxigênio, ocorrendo consequentemente a redução da atividade metabólica da biomassa, verificada com a redução dos valores de eficiência de nitrificação. Estes resultados evidenciam que a técnica de respirometria apresentou-se como uma ferramenta eficaz e segura para avaliação da toxicidade da biomassa do lodo ativado, sendo capaz de detectar a queda da atividade celular na presença de inibidores, como elevadas concentrações de salinidade.

Biological nitrification in a saline medium was investigated in a continuous system of a synthetic effluent containing 152.44 mg L-1 of total ammonia nitrogen. Tests were performed with the addition of increasing concentrations of salt (100, 250, 500, 1,000, 2,000, 4,000, 8,000, 10,000 and 15,000 mg Cl- L-1) in a 5.7 L laboratory bioreactor. The objective of the study was to evaluate respirometry technique responses in order to identify toxicity in nitrifying biomass with varying salt concentrations. During the experiment, the bioreactor was operated with a hydraulic retention time of 48 h, and DO, pH and temperature maintained at 4.0-5.0 mg L-1, 7.5 and 25°-30°C, respectively. The respirometric assays were performed in triplicate, using a dissolved oxygen probe. The results of respirometry found that both oxygen uptake rates (OUR) and specific oxygen consumption (SOUR) increased up to a concentration of 1,000 mg Cl- L-1, when the nitrification efficiency maximum of 65.18% was obtained after approximately 90 days of system operation. However, a gradual increase to 2,000 mg Cl- L-1 resulted in a decrease in oxygen consumption values, reducing the metabolic activity of the biomass, as verified by a reduction in nitrification efficiency values. The results show that the respirometry technique is an effective and reliable tool for assessing the toxicity of activated sludge, and that it is able to detect a decrease in cellular activity in the presence of inhibitors, such as high concentrations of salinity.

ELISA in situ can be used to titrate hepatitis A virus (HAV) particles and real-time polymerase chain reaction (RT-PCR) has been shown to be a fast method to quantify the HAV genome. Precise quantification of viral concentration is necessary to distinguish between infectious and non-infectious particles. The purpose of this study was to compare cell culture and RT-PCR quantification results and determine whether HAV genome quantification can be correlated with infectivity. For this purpose, three stocks of undiluted, five-fold diluted and 10-fold diluted HAV were prepared to inoculate cells in a 96-well plate. Monolayers were then incubated for seven, 10 and 14 days and the correlation between the ELISA in situ and RT-PCR results was evaluated. At 10 days post-incubation, the highest viral load was observed in all stocks of HAV via RT-PCR (10(5) copies/mL) (p = 0.0002), while ELISA revealed the highest quantity of particles after 14 days (optical density = 0.24, p < 0.001). At seven days post-infection, there was a significant statistical correlation between the results of the two methods, indicating equivalents titres of particles and HAV genome during this period of infection. The results reported here indicate that the duration of growth of HAV in cell culture must be taken into account to correlate genome quantification with infectivity.